<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        #canvas {
            background: #000;
            width: 400px;
            height: 400px;
        }
    </style>
</head>
<body>
<canvas id="canvas">

</canvas>
<script>
    var canvas = document.getElementById("canvas");
    var context = canvas.getContext("2d");

    context.beginPath();
    context.arc(100, 100, 50, 0, Math.PI * 2, true);
    context.closePath();
    context.fillStyle = 'rgb(255,255,255)';
    context.fill();
</script>
</body>
</html>